Well maybe there have been more than 10 since then

but a quick internet search turned up a Smith & Wesson M&P15 being used in Aurora.
I was wrong. The shooters in Aurora and Colorado used semi auto rifles.
1. Va Tech - shooter used a Glock 19 (pistol) and Walther P22 (pistol)
2. Luby's in Kileen, TX - Glock 17 (pistol) and Ruger P89 (pistol)
3. San Ysidro McDonalds - Uzi, Winchester 12 gauge shotgun, and Browning HP (pistol)
4. University of Texas - rifle
5. Edmond, Ok Post Office - Two 1911's (pistols) and Ruger .22lr (pistol)
6. Columbine - we all know the guns used
7. Immigration Center Binghamton, NY - Baretta 9mm (pistol) and Barreta .45 (pistol)
8. Fort Hood - FN Five-Seven (pistol that shoots rifle rounds) and Smith & Wesson .357 revolver
9. 1949 Camden NJ - Luger P08 (pistol)
10. Aurora - M&P 15 ("assault rifle"), 2 Glock 22 (pistols), and Winchester pump action shotgun.
This list was complied before Newton.
Sorry for the typos. Helping the intern prep his first 1040.