There were 48 ambush-style incidents where officers were shot without any warning or opportunity to defend themselves, including several pre-planned assassinations.
In many cases, officers were shot before they could exit their vehicles after an initial traffic stop or upon arrival at the scene of an incident.
Some articles on this topic:
Law Enforcement Officers Shot in the Line of Duty 2020 Year-End Summary
Ambush Assaults on Officers Rise in Criminally Emboldened Environment