Some stuff that confuses me in this sentence

会社員の男が男性の腹を踏みつけるなどし­て死亡させた疑いです
Okay , so here after the 踏み we have つける.
But what does exactly does it means here?
Also why is the な after that?
Last one, させた, I don't seem to get what exactly the verb させる is used for.

Maybe some newbie questions but I'm self-studying and although I have learned much of simple/daily vocabulary & expressions, I still have trouble understanding some simple stuff.

Any help appreciated,
Thanks in advance!

[会社員の 男が 男性の 腹を 踏みつける など して 死亡させた] 疑いです

踏みつける is one verb meaning "to stomp on (something/someone).
な is part of など, meaning "etc." "among other things"
死亡する means "to die," so 死亡させる means "to make/cause (someone) to die."

- The suspicion is that a male company worker stomped on another man on the belly (among other violent act he committed) which led to his death.

In general, the 〜あせる form of a verb is called the causative form. As AK said, it can mean "to make someone to (do something)", but it can also mean "to allow". Something like お母さんが娘に野菜を食べさせた can mean either "The mother made her daughter eat vegetables" or "The mother allowed her daughter to eat vegtables". You have to guess from the context which one is meant (here it is not too difficult).

The general pattern is う becomes あせる for godan verbs and る becomes させる for ichidan verbs. The causative forms conjugates as an ichidan verb.

Thank you very much!