Union City standoff with armed man ends in his arrest, police say

After a prolonged standoff City Tuesday, police arrested an armed ex-boyfriend of a woman whom he allegedly held captive.

The man, identified as Mario Martinez, 38, of Union City, had refused to surrender for hours after the woman, who told police she had been held against her will for two days, escaped shortly after 8 a.m. Tuesday. Authorities deployed a SWAT team before Martinez was eventually taken into custody about 3 p.m.

Officers had been at the home in the 33900 block of Railroad Avenue, where the woman was reportedly held, since about 8:20 a.m. Tuesday, according to the Union City Police Department.

Inside, the suspect spent much of the day holed up with a shotgun as he refused to leave, ignoring negotiators who tried to bring the standoff to a close, police said.

Authorities instituted a shelter-in-place order for the area that continued Tuesday afternoon. Some of the immediate neighbors were evacuated, police said.

Police arrested Martinez without any injuries reported to the suspect or officers.

He was taken into custody by the Fremont Police Department — which assisted in the operation, along with officers from Newark and Hayward — a spokesman said. Martinez was booked on suspicion of kidnapping, false imprisonment, assault with a deadly weapon, making criminal threats, and being a prohibited person in possession of a firearm.

The woman was able to escape the home, but then her ex-boyfriend barricaded himself inside and refused to surrender, police said. A SWAT team was on scene to negotiate with the man, police said.

Martinez struck his estranged girlfriend with the shotgun while he held her captive as he threatened her, the woman told police.

Officers initially responded to the Union City home when the woman dialed 911 and whispered a plea for help before the line went dead, police said.

Michael Bodley is a San Francisco Chronicle staff writer. Email: mbodley@sfchronicle.com. Twitter: @michael_bodley