Michael Madsen‘s sons are gathering exterior his Malibu house the place he was discovered lifeless … the feelings are popping out, and it is all on video.

The ‘Kill Invoice’ actor’s 4 sons — Christian, Max, Luke and Kalvin — hugged and embraced Tuesday at their father’s property … and so they look somber and unhappy.

As we reported … Michael was discovered lifeless inside the home Thursday morning after somebody known as 911 to report him unresponsive. LASD deputies arrived and pronounced Michael lifeless on the scene.

Michael’s dying is sending shockwaves by means of Hollywood and his actress sister Virginia Madsen and others he labored with are sharing fond recollections and heartfelt tributes … together with Vivica A. Fox and Jennifer Tilly.

The official reason for dying is unclear, however legislation enforcement sources inform us no foul play is suspected and it seems he died from pure causes. Michael’s rep Liz Rodriguez tells us he suffered cardiac arrest.