The search is underway for the gunman responsible for killing three people Thursday morning in the Bronx.

Shots rang out around 9 a.m. outside the Shore Haven Diner on Castle Hill Avenue. 

Two 33-year-old men, identified as Mustafa Tarver and Christopher Alleyne, were shot in the head and died at the scene.

A 45-year-old female bystander, identified as Arileida Jimenez, was shot in the back. 

She was taken to Jacobi Medical Center where she also died. 

Witnesses say the victims were well-known in the area. 

"The gentleman is a regular guest at our diner, came in asked to use the bathroom and then left and got shot dead right in front of our diner. They are good people, not even in any drama or anything," said one witness.

Maria Nuñez, a friend of the two men who were killed, says she doesn’t know why they would be targets.

"They’re not even people that get into drama or nothing. They’re just good innocent people," Nuñez said.

The shooting prompted a brief lockdown at nearby PS 36. 

The Castle Hill area has had four shootings this year and four in 2017.  

Police say the shooter fled on foot.

They say a "vigorous investigation" is ongoing.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-8477, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.