The hunt is on for a gunman who police say sprayed two North Philadelphia blocks using a high-powered assault rifle in separate shootings that killed one and wounded three others earlier this month.

"We've already had one person killed and three others shot," Homicide Unit Capt. James Clark said during a news conference Friday. "Quite frankly, we could have a lot more killed."

In the first shooting, surveillance video shows two men walking near the corner of 7th and Venango streets shortly after 10:30 p.m. April 6. Another man, wielding what police say is an AK-47 rifle, runs up to the pair and opens fire, hitting both men. Tyrone Rosser, 36, was shot several times and later died at Temple University Hospital, Clark said. The second victim, a 42-year-old man, was treated for a gunshot wound to the leg and released.

Police said they recovered 22 high-caliber casings at the scene, and the shooter can be seen wildly continuing to fire the gun as he runs west on Venango Street and north on 8th Street.

"As he's running away, he's sort of just firing in the air, so he's a very dangerous person," Clark said. "We have to get him off the street as quickly as possible."

A week later, on April 13, a gunman matching the description of the gunman opened fire on two men at 7th and Clearfield streets – about seven blocks from the scene of the first shooting. Police said the 23 shell casings recovered at that scene matched those found at the scene April 6. Both victims in that shooting, men aged 19 and 36, survived their gunshot wounds, said 25th District Capt. Frank Vanore.

Surveillance video from the second shooting shows sparks flying as bullets ricochet off the street and buildings and the victims running to escape the gunfire.

The shooter is described as a black man between 5 feet 6 and 5 feet 8 with a thin build. He wore a white hooded sweatshirt in both instances.

"We need to get that weapon, and we need to get the person using it," Police Commissioner Charles Ramsey said.

Ramsey said in addition to the $20,000 reward offered for a tip leading to an arrest and conviction in any homicide, the Mayor's Office and the Fraternal Order of Police each kicked in a $5,000 reward to get the gunman and the weapon off the street.

"It has no purpose, no place in on the streets of our city at all. You think you're looking at Iraq instead of Philadelphia when you're looking at that," Ramsey said. "It's absolutely insane."

Anyone with information should contact the Homicide Unit at 215-686-3334, the police tip line at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or submit a tip online. Tipsters may remain anonymous.

Video: Firearms Identification Unit Lt. Joseph Walsh demonstrates an AK-47 like the one believed to be used in the shootings.