In the non fiction book;
No Heroes, about how the FBI's elite Hostage Rescue Team(HRT) was started & run, the FBI had the team members who were trained in first aid/medical support placed in major US city ERs/trauma wards to learn first hand how to handle gun shots, cuts, burns, etc.
Many US Air Force ParaRescue & US Army SF(spec ops) send medics to cross train in major US cities too.
That's a smart move. Young team members get real world skills & learn how to deal with stress/injury/ERs.
As for rendering aid to armed felons or attackers, I would say;
no.
Unless you are a MD or RN & can explain your actions in court or a death investigation, Id wait for EMTs or fire-rescue.
As noted in the forum in other topics, former US Surgeon General; Richard Corona(who ran for the US Senate & was a SF medic in SE Asia), shot & killed a violent subject who attacked him as he ran towards a car accident to render aid.
Corona(check spelling) was a "SWAT doc". He was a combat veteran & trained in LE tactics in addition to his formal medical degree.
Clyde