Magnussen attempted an overtake on the Red Bull, taking Perez out and Hulkenberg who followed behind.
As a result the Red Bull of Perez was completely destroyed, with all three drivers out of the race and red flag promptly thrown.
The team have confirmed that Perez is back in the garage, and is safe after the crash.
Was Magnussen at fault for Monaco crash?
The stewards announced there would be no further investigation into the crash, which was good news for the Dane.
Magnussen is currently on 10 penalty points, and if the stewards had decided to penalise him he could have received a race ban.
The incident concludes what has already been a difficult weekend in Monaco for the Haas team.
Both drivers' were disqualified from qualifying due to exceeding the maximum 85mm opening in the wing for DRS.