No official word as the why, but apparently the location was known to be a drug distribution point. However a local paper was not shy in describing the who and why and to explain this is the 5th shooting of the yer in that neighborhood.

‎The fifth massacre of the year was staged today’s night in the vicinity of the residential Ernesto Ramos Antonini, in Río Piedras, where winds of war for control of drug trafficking was blowing about a month ago. ‎
The intense shooting that terrorized the area’s neighbors, who picked up on their cell phones the audio of the bursts, was reported past 7:00 p.m. when hitmen opened fire on a group in the communal area. ‎
‎According to information that emerged at the scene which is corroborated by the investigators, the victims could include an individual who was allegedly the target of the hitmen who was suspected of the shooting reported on the Day of Kings in the marginal Villamar on the grounds of a nightclub in the tourist area of Isla Verde‎.

Se registra quinta masacre del año en residencial Ernesto Ramos Antonini

I am still in favor of giving Puerto Rico its independence.