One of the most sought-after men in Puerto Rico remains behind bars in Berks County, police said.

Officers arrested Luis Santiago Castro in the 1200 block of Mulberry Street in Reading late Friday morning. Castro was arraigned Friday night and is now awaiting extradition to Puerto Rico.

Castro, 18, who also goes by the alias, "Trencitas," was being sought as the gunman in a homicide in Puerto Rico, police said.

"Here in Puerto Rico, we do consider him very dangerous, and he is one of the most wanted guys here," said Lt. Ferdinand Acosta, with the Puerto Rico Police Dept.

In April, while Castro was still 17, he shot and killed Juan David Lopez Aponte, 21, in the town of Yabucoa, Puerto Rico, investigators said.

The shooting may have been drug-related, and the victim was a mistaken target, Acosta said.

"We know for a fact that Mr. Juan David Lopez Aponte was not the intended target in this incident. He was fatally wounded, in front of his house, but we don't think he was the target in this situation," said Acosta.

Castro, officials said, is no stranger to the law, and he was already on the radar of federal authorities.

"He also was being investigated in the Syracuse area for other gang-related acts over there in New York," said Acosta.

Authorities in Puerto Rico said they have already started processing paperwork to have Castro extradited to Puerto Rico to face murder charges.