Israeli Air Defense systems operating in the North.

This came after heavy bombardment on Lebanon.

Israel has informed the United States prior to the preemptive strike against Hezbollah

More:

Sirens sound due to drone infiltration in nearly the entire border line all the way to the Golan Heights, in addition to more than 100 rockets were fired at Northern Israel so far. and:

Netanyahu and Galant led the attack against Hezbollah from inside the fortified underground headquarters in Kiryah in Tel Aviv.

and: 

Hezbollah announces the launch of retaliatory operations in response to the assassination of Fouad Shukr and a number of civilians and children in the southern suburb of Lebanon. 

Hezbollah releases an official statement regarding the retaliatory strikes: 

- We launched a drone attack towards the Zionist depth and on a sensitive military target that will be announced later

- Simultaneously, we targeted a number of enemy sites, barracks, and Iron Dome platforms in northern occupied Palestine with a large number of missiles.

- Military operations will take some time and details will be announced later.

- The resistance is at its highest level of readiness, and if the occupation harms civilians, the punishment will be severe and harsh.