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."

The lawsuit, filed in federal court in San Diego, seeks unspecified damages.

Jackie Wasiluk, a spokeswoman for U.S. Customs and Border Protection, said she would not comment on pending litigation. San Diego police have said an unnamed CBP officer fired the stun gun.

Iredale said the U.S. Justice Department's civil rights division is reviewing a San Diego police investigation to determine if criminal charges will be filed, and had not decided as of Tuesday. He said the U.S. attorney's office in San Diego recused itself because of its close relationship with the agencies involved.

The government denied the family's administrative claim for damages last month, a required precursor for a lawsuit. Iredale said he will now gain access to police reports and names of the agents involved.

The San Diego County coroner has ruled the death a homicide. The cause was determined to be a heart attack, with methamphetamine abuse and hypertension listed as contributing factors.

Hernandez had lived in the San Diego area for more than 20 years, according to the lawsuit. He is survived by his partner, Maria Puga, and their five children, ages 4 to 20.

Relatives have told the American Friends Service Committee that Hernandez was deported last May after being stopped for a traffic violation in San Diego. He returned to the U.S. through the rugged mountains east of San Diego and was arrested by the Border Patrol. He was being escorted back to Tijuana, Mexico, when he was shot with the stun gun.