They targetted another apartment block being used as a headquarters for the press - no Hamas there
From "Russia Today"
The Al-Sharouk compound, which houses many media offices in Gaza, has been targeted once again in an Israeli airstrike. Islamic Jihad says one of its top leaders was killed in the attack.
A pillar of smoke was seen billowing from the 10-story building as fire engines and ambulances rushed to the scene. Islamic Jihad says one of its top militant leaders, Ramiz Harb was killed in the strike on Monday. Harb is a leading figure Islamic Jihad's militant wing, the Al Quds Brigades. The IDF described Harb as a chief propagandist for the mlitant group.
The Israeli Defense Force (IDF) confirmed via Twitter that four Islamic Jihad operatives who were hiding in a media building were the intended target of the attack on Monday. Several people are also reported to be wounded.

"The senior PIJ [Palestinian Islamic Jihad] cadre was operating in a media building. They were't [sic] there to be interviewed. They were using reporters as human shields," the IDF tweeted.
"We targeted only the 2nd floor, which is where the senior terrorists were. The rest of the building was unharmed. Direct hit confirmed," they continued.
Apart from Harb, Baha Abu al-Ata Tissir, the commander of Islamic Jihad's Gaza City Brigade, and senior operatives Mahmoud Mahmed Jabari and Halil Batini were believed to be in the building at the time of the attack. It is currently unknown if the other three men died in the attack.