Philadelphia mass shooting leaves investigators searching for answers

Investigators are searching for answers as to why someone wearing a ski mask and body armor went on a shooting spree in Philadelphia on the eve of the Fourth of July, gunning down five people.

"This armed and armored individual wreaked havoc, firing with a rifle at their victims, seemingly at random," Philadelphia Police Commissioner Danielle Outlaw said during a press conference on Tuesday.

The Philadelphia Police Department received 911 calls about a shooting near Chester Street in the city's Kingsessing neighborhood on Monday night just before 8:30 p.m. ET. Gunfire was heard in several areas near the first location during the shooting, according to police.

Surveillance video obtained by Philadelphia ABC station WPVI appears to show a person shooting at a nearby intersection.

Kingsessing resident Theo James said he heard a young man screaming for "help" before realizing there were multiple gunshot victims.

"After I helped him out, I saw another person down the street, discovered them and helped them out. And one more person," James told WPVI.

Five people died after being shot multiple times, according to police. The victims were identified by police as Daujan Brown, 15; Lashyd Merritt, 20; Ralph Moralis, 59; Dymir Stanton, 29; and Joseph Wamah, Jr., 31.

Lashyd Merritt's mother, Marie Merritt, said her son was headed to a store across the street from their home when he was shot dead, telling WPVI: "It's like I feel him saying, 'Why me, why me, why me?'"

Two unidentified children, as young as 2, were injured during the shooting while Traveling in a car with their mother. One suffered an eye injury from shattered glass and the other was shot in the leg, according to police.

Police said responding officers came under fire as they pursued the suspect that night, arresting the 40-year-old in a rear alley of Frazier Street after a brief chase on foot. The officers did not return fire and the suspect ultimately surrendered, police said.

The alleged shooter had been using an AR-15-style rifle, which was recovered by police. A 9 mm handgun, magazines and a police scanner were also found on the individual, according to police.

The unnamed suspect is currently awaiting arraignment. Philadelphia District Attorney Larry Krasner told reporters Tuesday that the person "will be facing multiple counts of murder and will also be facing multiple counts of aggravated assault as a first degree felony weapons charges, among others."

Police said they are not formally naming the suspect until criminal charges are filed, which is expected to happen sometime on Wednesday.

Multiple law enforcement sources told ABC News that the suspect is Kimbrady Carriker.

ABC News' Victoria Arancio, Trevor Ault, Joshua Hoyos, Aaron Katersky, Josh Margolin and Jason Volack contributed to this report.