The report Wednesday on police radio was urgent, the rushed tone in a cop’s voice hinting at the terror that was to come: “3700 15th, assist the officer. Shots fired, shots fired.”

On that block of North 15th Street, just a stone’s throw from a busy SEPTA hub on Erie Avenue, a group of police officers had barged into a rowhouse about 4:30 p.m. to serve a warrant on narcotics charges. As they made their way to the rear of the property, they were met by thunderous gunfire. Some jumped through windows to escape the bullets, Police Commissioner Richard Ross later said.

“I got an officer shot at this location in the leg!” one cop yelled to a police dispatcher.

The dispatcher shared the assistance call once, twice, three times: “We got an officer down!” — a siren call that led dozens of police officers to rush to the scene, clogging the streets with their patrol cars, as news helicopters began thrumming overhead.

In the panicked and chaotic hours that followed, the number of wounded officers grew from one to six, and the eyes of citizens and politicians across the country became fixated on this pocket of Tioga, as the conflict morphed from an active mass shooting to an unthinkable standoff: the gunman barricaded inside the rowhouse, along with two police officers who were trapped with three people they’d arrested.

“How you doing inside?” a police commander asked one of the officers over the radio.

“I got full ammo, ready to go,” the cop responded.

The officers and their prisoners remained trapped inside the house until close to 10 p.m., when they escaped unharmed, with the help of the SWAT Unit. The standoff continued until midnight, when police fired tear gas into the property. Maurice Hill staggered outside with his hands in the air, as cops hollered at him to get down on the ground. He was quickly loaded into a waiting police van.

» CATCHING UP: What you should know about the Philadelphia police shooting and standoff

About 8 p.m., Ross spoke to reporters at Temple University Hospital, where some of the wounded cops had been admitted for treatment. None of the six had life-threatening injuries, he said, although a bullet grazed one officer’s head, and others had been shot in legs and arms. The officers’ names were not released, and all were later released from the hospital.

“Fortunately, everybody’s going to be OK,” Ross said.

Police thought for a time that they might have been dealing with two gunmen there was so much shooting.

“I’m a little angry about someone having all that weaponry, all that firepower, but we’ll get to that another day,” Mayor Jim Kenney said.

It was unclear whether Hill was the target of the warrant that the officers were serving. Hill, 36, has an extensive criminal history, with arrests on charges that included narcotics, attempted murder and resisting arrest, according to court records.

» READ MORE: Alleged shooter in Tioga standoff has a long criminal history

Officers who responded to the assist call nearly ran headfirst into the line of fire. “Male shooting out the back!" one commander yelled over the radio. "Everyone stay put!”

The two cops who ended up trapped in the 15th Street property with the shooter were wearing blue bike uniforms. They began precariously radioing their position to supervisors, who spent hours trying to figure out a way to bring the standoff to an end.

One commander was asked if an armored police vehicle could be allowed to smash through a line of patrol cars near the house. “Do what you got to do,” he responded.

“Be advised. We’re still pinned down inside this location,” one of the officers radioed shortly after 5 p.m. “The male is inside the kitchen shooting upward and forward to the opposition of the police.”

One cop was stuck in a rear bedroom with two prisoners, a man and a woman, while the other officer was holed up in a bathroom with a male prisoner.

The cops described hearing the gunman pacing below them, talking on the phone, then talking to himself.

Ross was outside, along with members of the SWAT Unit, clad in a bulletproof vest. “He started firing at us again,” he told a reporter shortly before 6 p.m.

Ross began personally pleading with the gunman to end the standoff peacefully.

The surrounding area, meanwhile, came to a standstill.

Temple University placed its nearby medical campus on lockdown. SEPTA officials instructed Broad Street Line trains to avoid stopping at the Erie, Allegheny, and Hunting Park stations, and several bus routes were detoured.

Neighbors close to the standoff were left paralyzed with fear.

Amanda Baker described to a reporter how she hunkered down, avoiding the windows in her apartment a few houses down from the one police had surrounded.

“I was watching TV, and I heard all this ruckus,” she said, breathing heavily while speaking on the phone. “Next thing I saw, there were cops with their guns drawn running past the window. This is the craziest thing I’ve ever seen.”

She said she’d been calling neighbors, who were coming home from work and alerting them not to come to the house.

“Each time I think it’s over, I start hearing gunshots again,” said Raphael Brown, who was waved back into his nearby apartment by police officers at the start of the standoff. “I must have heard over 50 gunshots sporadically.”

» PHOTOS: A neighborhood on lockdown, watching as police respond to standoff

A day-care center near the shooting scene was under lockdown until about 7:10 p.m., when police escorted 58 children and adults from the location.

Police officers carried babies, and mothers comforted shaken children as the day care was evacuated.

“We had to stay calm and collected, and get the children calm,” one staffer said.

Police had set up two city buses to hold children whose parents hadn’t yet arrived to pick them up. Other parents rushed frantically down the block, asking after their children at the bus doors.

“I’m just happy I got my daughter,” said Shere Calhoun, smoothing her 8-year-old’s hair. “I didn’t want her to be a victim.”

“Calm down, calm down,” an officer called to another parent running down the block. “The kids are safe.”

Wednesday’s incident marked the seventh mass shooting in the city so far this year, according to data compiled by the website The city’s homicide total stood at 203 as of Tuesday, a 4 percent increase from last year, while the number of aggravated assaults with guns had climbed 8 percent, to 1,552.

The wounding of six police officers in a flurry of gunfire was the most officers shot in one incident in recent Philadelphia history.

Forty-one years ago, five officers were shot — one fatally — when police clashed with the cult group MOVE in West Philadelphia. Authorities said shots from the barricaded MOVE compound fatally struck Officer James Ramp and seriously wounded other police. Four firefighters were also wounded by bullets during the Aug. 8, 1978, incident.

In a second confrontation with MOVE, in 1985, 11 people were found dead inside the cult’s fortified rowhouse on Osage Avenue, five of them children, after a fire started when police dropped a bomb on the house. No police were hurt in that daylong clash, which began with a lengthy gun battle.

In what at the time was called the bloodiest weekend in the history of the force, five police officers were shot, one of them fatally, on a Saturday and Sunday in the summer of 1970. In that episode, self-described black radicals fatally shot Sgt. Frank Von Colln in the Cobbs Creek Park police headquarters.

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Staff writers Chris Palmer, Mike Newall, Mensah M. Dean, Jeremy Roebuck, Claudia Vargas, Aubrey Whelan, Dylan Purcell, Andrew Seidman, Robert Moran, Craig R. McCoy, Pranshu Verma, Barbara Laker, and Samantha Melamed contributed to this article.