Ahmed Jabari, head of the Hamas military wing was driving along in a car in the centre of Gaza city in broad daylight. He plainly didn’t expect what was coming. Hassan Nasrallah, the leader of the Lebanese Shiite group Hezbollah, who knows he is an Israeli target, wouldn’t have done it. Nor would Hamas military leader Mohammed Deif, whose vehicle was hit in an Israeli air strike in Gaza in 2002; after crawling out from under the wreckage, he hasn’t been seen in public since.

Jabari was more confident. So, at around 4pm on Wednesday, an Israeli drone identified his car, and released its missile. It was a surgical strike. Jaabari and his driver were killed. No-one else was injured. Little remained of the car. We can see it all for ourselves, because after live tweeting the attack, the Israeli military released the tape of the hit. It shows fuzzy images of a street, with trees visible, and a car, circled. It’s moving until there’s a white flash and it’s blown apart. More strikes quickly followed.

Jabari was a powerful, charismatic outsider who had climbed to the top. His family had moved to Gaza from the West Bank as the result of a blood feud. He joined the opposition group Fatah, before moving over to Hamas while in an Israeli jail in the 1980s, back when Fatah began talking about making concessions to the Israeli occupiers. He had always been hard-line. Since the late 1990s he’d worked to transform the Hamas military wing from isolated terrorist cells into an organised fighting force. He had broadened its arsenal to include long-range rockets produced by Iran and smuggled into Gaza through Sinai (and recently via Libya.)

Jabari was responsible for masterminding the kidnapping of an Israeli soldier in order to negotiate the release of Palestinian prisoners. In 2006, his team tunnelled under the border from Gaza into Israel, killing two Israeli soldiers, wounding four more and taking one of them— Gilad Shalit — back into Gaza. This operation was carried out despite opposition from Hamas political leader Ismail Haniye. Jabari also took charge of the negotiations for Gilad Shalit’s release. He brought more than 1,000 Palestinian prisoners home, and became the unrivalled leader of Hamas and the Gaza Strip.

He said afterwards that the day which saw the prisoners released had been the happiest of his life. In a rare interview, on Egyptian TV, he said, “I am now confident regarding Hamas. I have established a powerful army, and Allah granted me the privilege of concluding the Shalit deal.”

His death was a body blow to Hamas. If surprise is the most crucial element in an attack, Israel’s military action began strongly. The reaction was immediate.

“The Israelis thought they could break Hamas resistance by killing al-Jabari. They are wrong. The Palestinian resistance is still strong,” said Hamas spokesman Sami Abu Zuhri. “Two days ago, there was a ceasefire agreement prepared through Egyptian mediation. The Israelis did not commit to it and now they will pay the price.”

Another Hamas official described Jaabari’s killing as an act of war. Another militant group said the gates of hell would open. Then Gaza began tweeting its protest.

In a bizarre twist, there were official tweets between two groups who don’t speak to each other, the Israel Defence Forces, and the Hamas military wing, Izzedine al Qassam. Both @idfspokesperson and @alqassambrigade took aim and fired.

That’s how it’s done these days. Tapes and threatening tweets.

But the online hostilities didn’t diminish the panic that ensued in Gaza city. There was the sound of explosions, fire engines and other sirens and crowds protesting on the streets. People were running, screaming, as the assassination was followed by waves of Israeli air strikes.

Israel’s defence minister Ehud Barak said his forces’ main targets were Gaza’s stockpiles of long-range Iranian rockets, such as the Fajr 5 missiles. These have a range of 75 kilometres and are capable of reaching Israel’s main population centres, around the city of Tel Aviv. According to military analysts, the Fajr 5 rockets were being kept in Gaza as “doomsday weapons”. The person who was supposed to give final authorisation for their use was Ahmed Jabari.

Israeli defence officials now claim the airstrikes have wiped out the majority of these stockpiles. But there’s always a wildcard in Gaza — say, the smaller militant groups who have smuggled in a few long-range missiles for their own use and kept them hidden. What happens if they start firing them? In the past few hours, the first such rocket attack hit Tel Aviv — the thing Israel was most determined to avoid. One was fired by a smaller radical ground, Islamic Jihad, the other by Hamas.

The price of any military action, particularly in this region, is high and the outcome unpredictable. Since Jabari's assassination there have been more than 250 rockets fired into Israel and three civilians have been killed. The retaliatory Israeli air strikes are continuing in Gaza, where so far 13 people have died. Children are among the dead and injured on both sides.

Uriel Sinai/Getty Images

A rocket is launched from Gaza into Kiryat Malachi in Israel. More than 250 rockets have been fired since Wednesday's killing of Hamas military leader Ahmed Jabari.

IN GAZA CITY, Dr Maher al Jirjawi had just checked his pregnant wife into hospital for high blood sugar when the Israeli air strikes began. He spent the night looking after his four children. But he’s an anaesthetist, and tomorrow he has to go in to work. The hospital has moved to on an emergency footing, so it’s a 24-hour shift. He will leave his children at home alone.

“Everyone is worried. People here are very afraid of war,” said Dr Jirjawi. “War is a catastrophe, for the people, not for the government. The people are the losers. The wanted man, he will disappear, but the people cannot run away, and they always suffer.”

In Gaza and southern Israel, people are hunkering down, braced for more clashes.

Irris Makler is the author of Hope Street Jerusalem. She blogs at hopestreet.com.au