VIENNA (AP) — An Austrian state prosecutor says his office is preparing multiple murder and terrorism-related charges against a Syrian man who reportedly says he killed badly wounded members of the Syrian army with bursts from his submachine gun.

Prosecutor Hansjoerg Mayr says the 27-year-old told others sharing a migrant shelter in the province of Tyrol that he killed at least 20 victims who were wounded during fighting in Syria to spare them from suffering.

Mayr said Friday proceedings were launched after the man, whom he described as belonging to a subgroup of the Syrian Free Army fighting government forces, told the same story to police.

He was not identified in keeping with Austrian privacy laws. Conviction on “the crime of murder as a terrorist crime” is punishable by a prison life sentence.