there are many possible causes. you should go see a doctor and get an ultrasound of your testicles plus some blood test --> cpr, blood count and maybe beta -HCG and AFP (alpha-fetoprotein).

This can only help (CAN not WILL) if the heart attack is accompanied by a irregular heart rhythm.

Best thing to do is to stay calm, call the emergency number, tell people around you, you might having a heart attack (so they can perform a CPR if necessary),rest and take 1 gramm of aspirin.

Im sorry for your loss.

Your uncle may have suffered a ruptured brain aneurysm which leeds to haemorrhage (bleeding) in the brain. If the aneurysm is pretty big or the bleeding is very severe, death will occur within minutes. The mortality (death rate) of ruptured aneurysm lies within 50% and is almost 100% without fast and proper neurosurgical intervention.

studies show that around 2-5 % of the world population carry such an aneurysm, but it will only rupture in 10% of the 2-5% who have it.

Risk factors which increase the risk of developing an aneurysm or a rupture of a existent aneurysm are smoking, being black (studies in the us show that african americans have a 2.1 higher rate), being female (1 to 5 ratio) and alcohol abuse.

Theres also a genetic risk if other family members carry an aneurysm. It can be detected best by magnetic resonance angiography (MRA).

So yes, it is possible for a 45 old man to "slump and die". Did your uncle have any symptoms in the weeks/days before he died, like dizziness, headache, blurred vision, etc ?