JERUSALEM, Israel - Hamas and other Gaza-based Palestinian terrorist organizations launched more than 120 rockets and mortars on southern Israel before agreeing Monday morning to a tentative ceasefire.

Israel stepped up air strikes against terrorist targets in the Gaza Strip after Hamas fired an anti-tank missile at an Israeli school bus driving near Gaza on Thursday, critically injuring a teenage boy.

According to reports, 19 Hamas and Islamic Jihad terrorists and two civilians have been killed in the Israeli air strikes.

Hamas appears to have agreed to the ceasefire because of Israel's tough response and the success of its Iron Dome missile defense system.

The Iron Dome's debut on the battlefield was successful, intercepting 100 percent of the longer-range Grad-type missiles launched at larger Israeli cities, such as Ashkelon, Ashdod, and Beersheva.

"This is a great technological achievement. It's the first time these types of missiles have been intercepted by Israeli technology," Prime Minister Benjamin Netanyahu said.

Netanyahu praised the engineers and soldiers operating the system, but warned the system couldn't protect everyone.

"We're in the first stage, but we went out in a sprint," Netanyahu said. "We'll still have developments of this system, but we can't cover every house, every citizen [or] every site in Israel," he said.

Still, many civilians were encouraged by the Iron Dome's successful debut.

"Before, it was scarier," said Shai, a resident of the coastal city of Ashkelon. "You heard a siren [and] you needed to jump into the shelters. Now you hear it [an air raid siren], you stop and look up. It [a missile] explodes and that's it," he said.

For now it's quiet, but no doubt both sides are preparing for the next round.