PHILADELPHIA (CBS) — Three people are dead and one other is injured following a shooting in North Philadelphia Monday afternoon.

It happened on North 11th and West Stiles Seeds around 3:30 p.m.

“We were in the school and all you hear is gunshots. Multiple gunshots,” said Awtum Mintze.

Mintze, 12, was inside St. Malachy with her 11-year-old sister Alycia for track practice when almost two dozen shots were fired at this apartment complex across the street.

“We had to stay in our classrooms. We couldn’t just walk out. We had to stay in the place we were in,” said Alycia.

Police tell CBS3 four men were standing outside on a sidewalk when a car came up, and began firing multiple shots. There were at least 21 shell casings on the ground.

Three of those victims lost their lives.

“Right now, we don’t know what we have. We had four individuals who were standing there. We believe that someone came east from this location and started firing. One shooter, maybe two, started firing at the individuals and then fled from this location,” said Philadelphia Police Capt. James Clark. “Right now, we don’t know what it’s over.”

Authorities believe the suspects and victims knew each other.

Alycia Mintze and her sister are safe–and her dad is thankful but worried what might have been.

“Life is valuable and precious. You only get one so we should make the best of it,” Andre Mintze said.

Police believe the suspects left in a small grey SUV.

If you have any information, give police a call at 215-686-TIPS.