PHILADELPHIA (CBS) — Philadelphia police have identified a teenage girl who they say stabbed two sisters, one fatally, in the Brewerytown section of the city on Monday. Police are searching for 19-year-old Tianna Thomas.

suspect Tianna Thomas Woman Killed, Sister Wounded In Double Stabbing

Police have issued an arrest warrant for Thomas in connection to the murder of 23-year-old Shawntae Garrison and the attempted murder of Garrison’s sister, 28-year-old Tayshawn Layton.

Layton is now out of the hospital and back home.

The double stabbing happened at 29th and Jefferson Streets on Monday around 11:30 p.m.

Police say Thomas is caught on a surveillance camera, with a group of seven other females, carrying out the attack.

“An altercation ensues, at which time we believe to be Tianna Thomas, is observed standing over Ms. Garrison, repeatedly stabbing her as Ms. Garrison is lying on the ground,” Philadelphia Police Capt. Jason Smith said.

Smith urged Thomas and the seven other females to turn themselves in.

A relative previously told CBS3 the stabbing stemmed from a fight over an Instagram post, but police have not been able to corroborate that claim. Smith said the motive appears to be a neighborhood dispute.

Thomas will be charged with murder, aggravated assault and other related offenses.