Hamas has tried for months to enforce informal cease-fire understandings with Israel — which Palestinian Islamic Jihad has often disrupted with rogue rocket or sniper attacks — in return for cash from Qatar. It now has to decide whether to raise the stakes by joining the group in avenging Mr. Abu al-Ata’s death, or to stand down in hopes of restoring calm.

Hamas said that it, too, mourned Mr. Abu al-Ata’s death and that his killing would not go unpunished, but the group stopped short of saying it would join the fighting.

The Israeli military said Mr. Abu al-Ata was to blame for rocket fire on Nov. 1 and in August, and said he was being closely monitored recently because he was planning a specific new attack against Israel.

His name had cropped up frequently in the reporting of Israeli military correspondents — which an army spokesman, Lt. Col. Jonathan Conricus, said was no accident, and was meant as a warning.

But some Israeli analysts suggested that an incident on Sept. 10, a week before the last Israeli election, may have sealed Mr. Abu al-Ata’s fate: When Mr. Netanyahu made a campaign stop in Ashdod — at a location announced in advance, breaking with customary security precautions — a rocket attack sent the prime minister and his entourage scurrying offstage to shelter.

Amit Segal, a commentator on Israel’s Channel 12, wrote on Twitter that there had been an “invisible laser marker” on the heads of both Mr. Abu al-Ata and his Damascus superior from that moment.

Militant groups in Gaza have clashed with Israel several times in recent years, with the last deadly conflagration taking place over several days in May. A devastating war in the summer of 2014 lasted 50 days and ended with a fragile cease-fire that has since been broken many times.