An air carrier pilot reported NMAC with VFR traffic while on initial climb out.

Narrative

Departing runway 12R at Mesa Gateway; shortly after climbing through 2000 feet we heard the tower controller reprimand a student pilot for doing something contrary to what he was told to do. At the same time we noted two targets directly in front of us and one went to a TA followed by the second going to a TA and the first going to an RA all within about four or five seconds. We also got a second climb announcement as we were already pulling 5000 ft./min. climb with auto pilot and flight directors off. The aircraft were so close that even on a range of 10 they were underneath the aircraft on the ND and we couldn't even see the altitude which we knew was within 400 feet from our initial observation of the targets.After the tower controller was done speaking to the student pilot. The controller said; Aircraft X if you are still there contact departure ". As we contacted departure; we got the RA followed by the climb again RA. The traffic was almost right underneath us when we got the RA. We went over the top of the targets and leveled at 8000 feet after being given clearance to climb to 8000 feet when we announced we were responding to the RA.It is unsure the exact distance as we were in a very steep clime and could not see out in the front windshield; but we did notice at least one target was within 400 feet of our aircraft as it approached us before it turned orange on the display.This airport gets multiple TCAS TA's. I feel confident the RA events are high as well. The concern is the totality of threat factors at this airport. 121 operations; Heavy fire fighting tankers; several biz jet service centers serving multiple various bizjets; air ambulance; 125 charter operations; transient military operations; 135 charter operations; upset recovery/aerobatic operations; and no less than 3 significantly large flight schools. The airspace is only Class D; and the airport may not even have radar on site.Suggestion: Radar; Class C with radar and arrival and departure routes for training aircraft as well as no practice approaches during hours of 0600-2300LCL."