PHILADELPHIA (CBS) — Police have issued an arrest warrant for 18-year-old Quintis Clark in the murder of 78-year-old Joseph Daly in Southwest Philadelphia.

Captain James Clark with the homicide unit says the body of 78-year-old Joseph Daley was found Tuesday afternoon inside of his home in the 6300 block of Theodore Street in the Elmwood section of the city. Officers responded after neighbors called police to say they haven’t seen him around lately.

Authorities say the cause of Daley’s death appears to be strangulation and blunt force trauma. They add that they believe that Clark tried to rob the victim just days before his body was discovered.

“We actually found his van up in the Northeast,” Clark said of discovering Daley’s stolen van. “As a result of that, we saw some video of one of the doers getting out of the van.” Police believe that was Clark.

Police say Clark has friends and family in the Northeast and that he is from Southwest Philadelphia, from the same neighborhood where Daley was found dead.

“He was seen getting out of the victim’s van. We had a couple people come forward and put him inside of the house at the time of the murder,” Clark said.

Officials say that Daley’s back windows of him home were broken and the believe the motivation was robbery. One neighbor says the news brings some relief, but that they’ll feel more comfortable when Clark is in custody.

Initially, it was reported that witnesses saw multiple people leaving the victim’s home and the investigation is ongoing to determine if more people were involved.

Police are urging Clark to turn himself in.

Anyone with information on Quintis Clark’s whereabouts are being asked to call the Homicide Unit at 215-686-3334/35. His last known address is the 7200 block of Vandike Street.

Police are offering a $20,000 reward for information leading to an arrest and conviction.

Rahel Solomon contributed to this report.