This is a cop's worst nightmare.

Authorities say Downey police fatally shot the wrong man in its pursuit of an armed street- robbery suspect whose description matched the victim's.

The man's family was devastated and sobbing in TV news footage over the weekend.

A strange twist to this saga, however, is that if 31-year-old Michael Nida didn't do it, then why …

… did he seemingly act suspicious?

It all started early Saturday night when police were responding to calls of an armed robbery suspect and came across Nida, whom cops said “was acting almost like a caged animal,” according to what sheriff's Lt. Dave Dolson told KCAL9.

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(Downey cops shot him but sheriff's detectives are investigating the incident).

Nida is said to have jaywalked across a busy street as he headed to buy his wife cigarettes at Imperial Highway and Paramount Boulevard, according to KCAL.

Cops actually detained the guy not once but twice and each time he allegedly resisted and took off.

According to KNX 1070 Newsradio each time officers got him there wasn't enough time to pat him down and search him, so there was still some fear that he might have been armed.

The last time Nida ran he was shot, which was at about 7:20 p.m., according to cops.

Terri Teramura, who ID'd herself as Nida's sister, claimed:

… They shot him … in the back. Five times. Killed him.

No gun was found on Nida.

-With reporting from City News Service. Got news? Email us. Follow us on Twitter, too: @dennisjromero.

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