The Gunners secured a 1-0 win on the night and a 2-1 aggregate victory over Atletico Madrid to reach their first European final in 20 years.
Bukayo Saka's first-half finish — his second goal across the two legs — was the difference over the two matches, booking Arsenal a place in the final in Budapest on 30 May against either Bayern Munich or Paris Saint-Germain.
The flashpoint came in the 95th minute. With the ball out of play between the two dugouts, Berta moved toward the touchline and gestured urgently at referee Daniel Siebert, pointing to an imaginary watch to signal that time had elapsed. Simeone, already booked earlier in the evening, took immediate exception and marched toward the Italian, pushing him in the direction of the tunnel.
Fourth official Sandro Schärer stepped between the pair and members of both benches piled in to separate them.
The confrontation carried a particular charge. Berta spent 13 years at Atlético, joining in 2013 and rising to sporting director before departing for Arsenal last summer. During that spell he worked alongside Simeone to win two La Liga titles, the Europa League, the UEFA Super Cup and the Copa del Rey. The one achievement that eluded them together was the Champions League — they lost finals to Real Madrid in 2014 and 2016.
Berta will now work toward a first Champions League title with Arsenal while Simeone faces uncertainty about his own future at Atlético following their elimination.
Both managers were booked in the closing stages alongside Koke and Kepa Arrizabalaga. Riccardo Calafiori had to be held back by Arsenal's set-piece coach Nicolas Jover as tensions ran across both technical areas.
Arsenal's last Champions League final appearance came in 2006, when they lost to Barcelona in Paris.