Alleged Colorado supermarket mass-shooter not fit for trial: media
Ahmad Al Aliwi Alissa (Boulder Police Dept.)

The man charged with killing 10 people in a US supermarket shooting spree is not fit to stand trial, media reported Friday.

Syrian-born Ahmad Alissa, 22, is accused of indiscriminately gunning down his victims in a Colorado store in March.

He faces over 100 criminal charges, including 10 of first-degree murder, in connection with the mass shooting, for which neither he nor prosecutors have suggested a motive.

Boulder County Chief Judge Ingrid Bakke ruled Friday that Alissa must undergo mental health treatment before the case against him can proceed, the Denver Post reported.

The paper said no details were given in court about the nature of his health needs, but his attorney said it was a "serious mental illness."

Alissa's brother Ali has previously said his brother was "paranoid" and "antisocial."

Alissa was briefly hospitalized after being shot in the leg by police who responded to the attack.

One policeman, who was the first on the scene, was among the dead.

Colorado is no stranger to such violence, having suffered two of the most infamous mass shootings in US history.

In 1999, two boys shot and killed 12 classmates and a teacher at Columbine High School. The shooters died by suicide.

`Then in 2012, a heavily armed man stormed a movie theater in Aurora, murdering 12. The gunman is now serving a life sentence without the possibility of parole.

Few parts of the United States are untouched by mass shootings.

According to a tally by Gun Violence Archive, a non-partisan research group, of the over 19,000 gun deaths so far this year, more than 650 have been in mass shootings.

This week a 15-year-old boy was accused of using his father's gun to shoot dead classmates near Detroit, Michigan.

Such incidents routinely spark national outrage and calls for stricter gun control.

But despite widespread support for tighter restrictions, the calls usually fizzle out, quashed by the country's powerful gun lobby and right-wing politicians who say the measures would impinge on constitutional rights.