@PotomacBob
What kind of gun, and what kind of gunshot wound, could have the character back on the job within 3 months.
I would strongly urge that you have the character that gets shot wearing Body Armor.
What era does your story occur? This is extremely important in terms of firearms, ammo, body armor, medical treatment and physical therapy, all determining how long it takes to recover.
After c.1995 medical care in the USA becomes significantly better. After c.2006 (because of medical advances treating personnel surviving combat wounds) (both SWAGs) depending by where your character is shot, and where they get treatment.
Lacking any specific information, I will provide a generic answer. If you wish to post more information on this thread, or PM me, I am willing to provide more specific information.
{For my bona fides while neither a doctor, nor medic, I have received considerable training in the treatment of various traumas, mostly focused on battlefield and military training since civilian IFAT and then EMT from the early 1980's; then a couple years later training in the US Army. From the mid-80's I received training from Special Forces Medics, but I was never a Special Forces Medic! SF have training as a primary mission, and fantastic realistic Training is available from them.
Post 11 September 2001 I attended the "Combat Life Saver" Course and received addition medical training from 18Ds (SF Medics); it was remarkable the significant improvements in field care of trauma, both techniques and equipment.
I have treated both injuries and wounds. I was wounded several times myself, including non-penetrating wounds to my body armor/helmet. I have had to go through physical therapy to return to duty.) That and $3.25 will get me a cup of coffee at Starbucks.}
A generic answer (presuming post 1980): Have the assailant use a .22 Long Rifle caliber pistol, presuming they don't believe the Principal (VIP) is not wearing body armor. Presuming an assailant is willing to get very close 7 meters (21 feet) or less. .22LR pistols and ammo are easily available, typically 10 rounds in a standard magazine; minimal recoil, and not very loud even without a suppressor (on a big city downtown street), easy to conceal, and minimal recoil.
Even using standard ammo it can be deadly, multiple shot trauma (multiple bullets striking a person) to their torso; to include upper thighs; similar to being hit by several OO pellets from a shotgun.
Potential wounds/injuries to your MC: pistol bullet striking their upper torso, off center, resulting in a cracked rib. Even commonly available Class IIA soft (concealable) body armor will typically prevent a bullet from penetrating, but only distributes the impact over a larger area. (Some people compare it to being hit by a baseball bat.) Perhaps a second bullet striking below where the body armor covers (most only protect the vitals aka upper torso; trauma plates usually only protect a rather small square or rectangle in the center of the torso front {and back, if wearer is smart}) So, say a "through and through" bullet passing through their body low on their torso, say just above their hip, without striking any vital organs.
Injuries cause by being punched, kicked by the assailant, or trampled upon by other bodyguards, security, or just hustling out of there. A misstep upon a stair, or even a curb, may cause foot or ankle injuries.
For your research, I recommend going to websites covering the Physical Therapy of LEO (Law Enforcement Officers) who have been shot. Often these LEO will have suffered more serious wounds than you want, however, those types of injuries you may want for your story are often "additional" wounds, and their physical therapy is discussed as part of the recovery process.
Go to the Second Chance body armor web page, they used to publish a newsletter of people, mostly LEO who survived due to their product. https://safariland.com/ (acquired Second Chance c.2005)
https://rtstactical.com/pages/dtp-home
https://www.bodyarmornews.com/
https://www.ntoa.org/
https://forum.officer.com/