From [HERE] SAN DIEGO -- The family of a Mexican man who died after a U.S. immigration agent shot him with a stun gun sued the federal government Wednesday, saying authorities used excessive force.

The wrongful-death lawsuit says up to 25 agents beat Anastacio Hernandez as he lay on the ground at a San Diego border crossing May 28, some stepping on the back of his knees as he cried for help. An agent allegedly silenced the 42-year-old construction worker by shooting him several times with the stun gun.

Family attorney Eugene Iredale said key evidence includes a witness' cell-phone audio of Hernandez crying for help and a witness telling agents to stop.

"This was a man who was frightened and who was really, at the time, pleading for his life," Iredale said at a news conference that was organized by the Mexican consulate in San Diego.

Mexican President Felipe Calderon has vigorously denounced the incident, saying a death "with that degree of violence is a truly unacceptable violation." The consulate said in a statement Wednesday that the Mexican government "reiterates its strongest condemnation of the incident that led to the death of one of its citizens."