Follow CBSPHILLY Facebook  | Twitter

PHILADELPHIA (CBS) — A powerful explosion rocks an apartment building in West Philadelphia. It happened around 11 p.m. at the Sheldrake Apartments on 49th and Spruce Streets.

Police say a 56-year-old man mixed gun powder and dynamite, causing the explosion.

2 Men, Woman In Custody After Body Found Wrapped In Blood-Soaked Carpet In Wissinoming Home, Police Say

Twenty people were evacuated and placed on a SEPTA bus to stay warm during the investigation.

A neighbor says he thought the loud noise came from a gas explosion.

“We go out and the cops are coming out here and dragging a guy out. I saw the blood in his face and his arm. I was asking the officer and he said he was making some time of explosion,” the neighbor explains.

sheldrake apartments Man Accused Of Mixing Gun Powder, Dynamite In Explosion At Apartment Building In West Philadelphia

Credit: CBS3

Police: 2 Men, Woman Found Dead Inside Tioga-Nicetown Home

“And that shocked me because we were expecting, like, to be a bomb. We were thinking it would be the gas,” the man adds.

The suspect is now being treated for minor injuries.

Residents have returned to their apartments.