A spate of gun violence across the city claimed the lives of seven people and injured 18 over the weekend, making it one of the deadliest stretches of crime in decades, Philadelphia Police Department officials said Monday.

The violence — which included a quintuple shooting, two triple shootings, and three double shootings — pushed the city’s homicide count as of Monday morning to 185 victims, more than 30% higher than at this time last year, according to department data.

“You all know it was a pretty horrific weekend. We had a lot of violence. Detectives are working around the clock,” Chief Inspector Frank Vanore, head of the Investigations Bureau, said during an afternoon news conference at police headquarters. “I’ve been working here over 31 years. I’ve seen a lot of violence. This is more violence than I’ve ever seen. ... So we’re very concerned. We need people to put down the guns.”

Homicide Capt. Jason Smith said some of the bloodshed was fueled by drug turf battles, arguments, robberies, and retaliation for previous killings — a motive police believe was behind three of the weekend killings.

Smith said investigators need the public’s help to solve the crimes — the arrest rate for slayings this year is just 46%.

“It’s up to the community,” he said. “It’s up to these individuals who are committing these acts of violence. They have to take a step back and say: ‘Wow. Is it really worth it? Are we going to continue going in this direction?’”

Smith asked anyone with information about the crimes to notify the police at 215-686-3334, 215-686-3335, or 215-686-TIPS. Tips can also be left at phillyunsolvedmurders.com, he said. Those who provide tips that lead to the arrest and conviction of a suspect will receive $20,000 from the city, officials said.

So far, no one has been arrested in any of the seven slayings and one man was arrested in one of the nonfatal shootings, said Vanore, who added that detectives are culling through video evidence from the various scenes.

An arrest warrant has been issued in one of the slayings, but the suspect remains at large.

The shootings claimed 25 victims in 14 incidents. The victims, 22 males and three females, ranged in age from 17 to 64, and detectives recovered 121 bullet shell casings, officials said.

The weekend’s first fatal shooting happened just after 9 a.m. Saturday on the 1600 block of Granite Street. Police found Tyree Roundtree, 31, lying in the street with a gunshot wound to the back. He died shortly afterward. Police have issued an arrest warrant for Naheem Williamson, 25, who is on probation, has eight previous arrests, and an active warrant for domestic robbery and probation violations, Smith said.

Roundtree and Williamson worked at the same construction company, and police believe Williamson learned that the victim had about $1,500 to pay the company’s day laborers, and killed him for the money. Williamson is still at large, Smith said.

The second slaying took place at 7:54 p.m. on the 1700 block of West Ruscomb Street in Olney, where police found Sebastian Brown, 20 suffering from gunshot wounds to the head and face. Smith attributed the killing, which remains unsolved, to “group-related violence” in the area.

“A lot of retaliation. One murder leads to another murder … and it’s a continual cycle of violence,” he said.

The third fatal shooting was a triple shooting in which two people were killed at 1:39 p.m. Sunday in the 2800 block of North 21st Street in North Philadelphia. Police found three young men inside a bullet-ridden 2000 Nissan.

Khalil Burgess, 18, a passenger in the rear driver’s side seat, was shot fatally in the head. Nazir Veasy, 19, who was in the rear passenger side seat, was fatally shot multiple times in the torso. He was pronounced dead at 3:30 a.m. Monday. The third victim, an 18-year-old man who was in the front passenger seat, survived a gunshot wound to the left arm.

The lone gunman was in a car that pulled alongside the Nissan and opened fire, Smith said.

The fourth fatal attack claimed the most victims — five — and two of them died. The shooting happened Sunday at 4:18 p.m. in the 100 block of East Albanus Street in Olney. The motive is believed to have been retaliation, Smith said.

The two victims who died were found suffering from multiple gunshot wounds on the porch of a home. They were identified as: Markel Amir Smith Rafi, 23, and Samir Lindsey, 17. The three gunshot victims who survived were transported by private vehicles to hospitals, where they were treated for injuries.

The fifth fatal shooting took place Sunday at 11:37 p.m. in the 800 block of East Allegheny Avenue, where a man was killed in front of a store and two women were shot and wounded. Aaron Parker, 26, was shot multiple times in the torso and died of his injuries. Parker was the intended target, and the motive is drug-related, police said.

Smith said police believe some of the weekend’s shootings may be linked to earlier homicides.

“Individuals in these groups decide to take matters into their own hands rather than relying on us to do the job, rather than providing us with information that will help us solve these homicides,” he said. “That’s why we find ourselves in this continuing cycle of violence.”