The witness and Mr. Verdejo drove both vehicles onto the Teodoro Moscoso Bridge, which spans the San Jose Lagoon, near San Juan. According to the complaint, they tossed Ms. Rodríguez Ortiz into the water. Then, Mr. Verdejo shot at her with a pistol from the bridge, according to the complaint.
The two men abandoned Ms. Rodríguez Ortiz’s vehicle, which was found a day later. Law enforcement officials were able to use cellphone data to piece together where Ms. Rodríguez Ortiz had traveled and with whom she had spoken before she disappeared, according to the complaint.
The information from Ms. Rodríguez Ortiz’s phone led law enforcement officials to Mr. Verdejo, and the bridge, the complaint said. Surveillance video from the bridge shows a dark S.U.V. similar to Mr. Verdejo’s parking on the emergency lane of the bridge. It also shows “visible movement of at least one individual on the side of the vehicle.”
Mr. Verdejo was in custody on Sunday evening and is expected to make his initial court appearance on Monday, according to a spokeswoman for the F.B.I.
It was not immediately clear on Sunday evening if Mr. Verdejo had a lawyer. He could not be reached for comment.
Mr. Verdejo’s boxing record is 27-2, with 17 knockouts, according to Top Rank, a boxing promotion company in Las Vegas. Top Rank, which lists Mr. Verdejo as one of its fighters, did not respond to a request for comment on Sunday.
“The thoughts and prayers of Top Rank are with the family and friends of Keishla Marlen Rodríguez Ortiz, and with the people of Puerto Rico in this moment of mourning,” the company said in a statement on Saturday night. “We are profoundly disturbed by the news and will continue to monitor the evolution of the case as it progresses.”