SAN JUAN – Three people were killed and another was left brain dead in an armed clash in the southeastern Puerto Rican town of Cayey, police said Saturday in a statement.

The incident occurred Friday night in Cayey’s Buena Vista neighborhood when a shootout erupted for reasons still unknown, the Puerto Rico Police said.

The first fatality, identified as Jonathan de Jesus Coma, 19, was found by police inside a vehicle.

The other two men slain, identified as Joshua Ortiz Haddock, 19, alias Jao, and Juan C. Tapia Colon, 24, died while receiving first aid at Cayey’s Mennonite Hospital.

Meanwhile doctors said Saturday that Luis Antonio Rodriguez Rodriguez, 25, was left brain dead.

About 20 shell casings from weapons of different calibers were found at the scene.

More than 400 people had been killed on the island through June 11 of this year.

That was lower than the figure for the same period of 2011, a year that ended with 1,136 violent deaths, some 15 percent more than in 2010 and the highest number of murders since records began to be kept in 1940.

Authorities in Puerto Rico blame rivalries between drug dealers for a spike in homicides over the past few years.