BERLIN (AP) — German authorities are looking into the history of a Polish nurse suspected of killing and robbing a patient to see if he had any other victims.

Munich police have arrested 36-year-old Grzegorz Stanislaw Wolsztajn on suspicion of killing an 87-year-old retiree with insulin shots in February. Police say Wolsztajn confessed to stealing about 1,210 euros (,500) and two debit cards from the victim.

At least four other former patients were hospitalized with life-threatening conditions.

News agency dpa reported Wednesday that investigators have received 26 tips on the suspect’s past jobs as a nurse across Germany after releasing his picture and asking the public for help.

The case echoes that of a German nurse serving a life sentence for two murders who was in January charged with killing 97 other patients.