Police were called dozens of times in recent months about problems at Walter Wallace Jr.’s home, and had responded twice on Monday to reports of disturbances at the West Philadelphia house before two officers answered a third call and shot him as he approached them with a knife, according to law enforcement sources.

What happened during those earlier visits — including which officers responded and how much they knew about Wallace’s mental health problems — remained unclear Tuesday. Asked at a news briefing, Commissioner Danielle Outlaw declined to offer details about prior contact police had with Wallace, saying the incident remained under investigation.

But the confirmation of previous visits, by sources not authorized to publicly discuss them, fueled growing questions about the police response to what Wallace’s relatives have described as a mental health crisis.

A lawyer for Wallace’s family, Shaka Johnson, said that before the shooting, relatives had called 911 asking for an ambulance — not police officers — to help mitigate the 27-year-old’s spiraling condition. Calling the shooting “unjustified,” Johnson said that Wallace’s pregnant wife had told officers when they arrived that her husband had bipolar disorder.

“Officers who are properly trained should notice certain things when they arrive at a scene,” Johnson said Tuesday. “Especially when his wife tells you, ‘Stand down officers, he’s manic bipolar.’”

The revelations came as Wallace’s death continued to draw impassioned reactions from across the country. And in a year when police have killed Black people in a number of high-profile cases, sparking a national conversation about law enforcement’s role, Democratic presidential candidate Joe Biden and running mate Kamala Harris issued a statement saying they were heartbroken for Wallace’s relatives. President Donald Trump’s administration said it was following the investigation and prepared to deploy federal resources to Philadelphia to counter any violence.

Pennsylvania Gov. Tom Wolf, at the request of city officials, mobilized the National Guard in response to civil unrest that erupted Monday night and included looting and injuries to demonstrators and 30 police officers. Guardsmen were last present in the city in June, after days of demonstrations over the police killing of George Floyd in Minneapolis, as well as incidents of vandalism and property destruction.

Outlaw said additional police units would be deployed Tuesday night but protests and looting continued for a second straight night. Around 9:30 p.m., the city’s Office of Emergency Management urged residents in West Philadelphia, Kensington, Fairhill, North Philly, Fishtown, and Port Richmond to remain inside for their own safety.

As the unrest swelled, police said a double shooting that left two teens wounded in Port Richmond may have been connected to looting at Castor and Aramingo Avenues. They did not offer further details.

In West Philadelphia, hundreds of protesters marched through West Philadelphia toward a standoff with police at the 18th District headquarters.

Andrea Dingle, 31, of South Philadelphia, brought her four children to the front lines of the protest there, standing face-to-face with a line of officers holding riot shields.

“My son looks like Walter Wallace, he has mental issues like Walter Wallace, I am scared he will be killed like Walter Wallace,” she said, holding her 9-year-old son. “They are out here traumatizing us, they are scaring us.” In Northeast Philadelphia, police reported looting at stores at Aramingo and Castor Avenues.

John McNesby, the head of the police union, defended the officers' use of force Monday in the confrontation with Wallace and called on the public “to reserve judgment until this investigation is completed.”

Meanwhile, District Attorney Larry Krasner — who since taking office three years ago has charged two former officers with murder over on-duty shootings — said his office was in the early stages of determining whether Wallace’s death would merit charges. “We are not out to cover for anybody," Krasner said. “We are not out to get anybody.”

Wallace got married this month, according to relatives and his family’s lawyer. He was an Uber Eats driver, rapper, and father of eight whose ninth child could be born as soon as this week.

On Tuesday night, two of Wallace’s young sons stood in front of dozens of cameras and reporters, clearly shaken but praising their dad. One said: “And Black lives still matter.”

Wallace had been in and out of court for nearly a decade, with convictions for crimes including resisting arrest and robbery. Court records show that city judges routinely sought to get him mental health treatment.

During a Tuesday afternoon news conference, the police commissioner said that the department was “still backtracking to find out what the officers knew” when they arrived Monday afternoon at Wallace’s house on the 6100 block of Locust Street. Outlaw also said a new city program to put a behavioral health specialist in the police dispatch center only operates during limited hours, and that the assigned counselor was not in the radio room at the time of the afternoon call regarding a disturbance at Wallace’s house.

Law enforcement sources said that before Monday’s calls, police had received 31 radio calls since May concerning that address. Some calls were considered low priority, while others included reports of a person with a weapon, threats, or assaults, the sources said.

The first two calls to police on Monday were reports of domestic disturbances. Chief Inspector Frank Vanore said at the same news conference that the third call was a report of a man with a knife.

Two officers, who have not been publicly identified, got to the scene around 4 p.m. Video of the incident posted on social media showed Wallace holding a knife and walking toward them as they backed away. Wallace’s mother and several onlookers pleaded with police not to shoot, according to the video and witness interviews, and the officers urged him to drop the knife.

Wallace was several feet away from the officers when they each fired seven shots, according to Vanore. As Wallace fell to the ground, his mother rushed to him and begin swinging her arms toward the officers, the video shows.

On Tuesday night, Wallace’s father and namesake said outside that when he closes his eyes, he sees his son being “murdered, butchered” in front of him.

“We got good cops, we got bad cops in the system," said Walter Wallace Sr. "Everybody’s got to be held accountable for what they do.”

Another relative, Anthony Fitzhugh, 49, said a family member had called police Monday because Wallace was having a mental episode.

“I understand he had a knife, and their job is to protect and serve," said Fitzhugh, a cousin to Wallace. "By all means do so, but do not let lethal force be the means by which you de-escalate the situation.”

Outlaw said neither officer who fired was equipped with a Taser — which uses electroshocks to temporarily stun its target. According to a department spokesperson, 2,301 officers, or about a third of the force, have completed the proper training to carry Tasers and are required to carry them while on duty.

The U.S. Department of Justice in 2017 recommended that all Philadelphia officers be issued Tasers to carry at all times, a standard Outlaw said the department still aspires to meet.

She said the department had asked for additional money in its last budget request to “continue to outfit our officers with Tasers,” but did not provide details about how many might be purchased, or when universal adoption would be complete.

Protesters who took to the streets of West Philadelphia late into the night Monday overwhelmed police along the neighborhood’s central commercial corridor of 52nd Street. Some demonstrators set police cars on fire, committed vandalism, or broke into stores. Outlaw said that officers were hit with bricks and that one sergeant remained hospitalized after being struck by a pickup truck.

Many businesses across the city boarded up windows, or closed early Tuesday in preparation for a possible second night of civil unrest.

Staff writers Kristen A. Graham, Jeremy Roebuck, Samantha Melamed, Oona Goodin-Smith, and Robert Moran contributed to this article.