Mari, who is on loan from the Gunners at Serie A side Monza, was caught up in a stabbing incident at a Milan supermarket. One employee died and Mari had to undergo surgery on a back wound.
The following day, Mari posted a picture alongside his wife while also thanking well-wishers for their messages.
"After the hard moment we experienced yesterday, both my family and I want to communicate that fortunately we are all fine despite the circumstances, and we want to say thanks for all the messages of support and affection that we are receiving," he wrote.
Mari was on Sunday discharged from hospital and just hours later, Martinelli headed in Arsenal's opening goal against Nottingham Forest and was handed a Mari shirt to hold up during his celebrations.