The Diamond Ground

His name was Ivan. He was a Russian, hired assassin and he had one mission. This was about the easiest job yet, to murder a fourteen year old boy. But there was a catch, it had to look like an accident.
He turned another corner and strode down a small alley way, as he pulled his hat further down over his face.
"Yeah well, see ya tomorrow, Alex!" The call came from a medium sized house in a row of more medium sized houses, that looked like exactly the same, medium sized house.
A pair of boys past Ivan, who was carefully watching the boy disappearing inside the medium sized house. It was definitely him.
Black hair, green eyes and wearing a Holdon Hill uniform. Not forgetting his name was Alex.
Ivan made a bee-line towards Alex and shouted before Alex could open the door. Alex looked around, first mistake.
"Excuse me!" Shouted Ivan.
"Me?" He replied. He started walking towards Ivan, This was his second mistake.
But Ivan was quick and he lashed out to shove Alex against the wall, but his hand never made contact. Instead he doubled back in pain, he looked one last time before he blacked out, for the boy, but all he saw was the end of a gun - and nothing.
_______________________________________________________________________

That was kind of a draft. Please review because I want to make my writing better.

His name was Ivan. He was a Russian, hired assassin and he had one mission. This was about the easiest job yet, to murder a fourteen year old boy. But there was a catch, it had to look like an accident.

I would try: "..and he had one mission: to murder a fourteen year old boy. This was about..." OR "This was about the easier job yet: to murder a fourteen year old boy". Not so sure about the punctuation on the second one, maybe it should be a double dash.
Also, you use the word 'murder'. Murder is a crime, and people instinctively thing of murder as bad. But this narrative is coming from an assassin, and you'd think he'd think there wasn't much wrong with knocking people off. So maybe instead o murder try 'kill', 'assassinate'.

He turned another corner and strode down a small alleyway[no space methinks],[also, if you are going to use 'as' then you don't need to put a comma here] as he pulled his hat further down over his face.
"Yeah.[period?] Well, see ya tomorrow, Alex!" The call came from a medium sized house in a row of more medium sized houses, that looked like exactly the same,[no comma] medium sized house.
Medium sized house. Three times. Same sentence. Not necessary. Maybe just cut it down to two.

A pair of boys passed Ivan[where is Ivan standing, in the alleyway?], who was carefully watching the boy[which boy? You didn't mention a boy before, just a 'call'] disappearing inside the medium sized house. It was definitely him.
Black hair, green eyes and wearing a Holdon Hill uniform. Not forgetting his name was Alex.
Ivan made a bee-line towards Alex and shouted before Alex could open the door. Alex looked around--first mistake.

"Excuse me!" shouted Ivan. [you already said he shouted, for readers its like deja vu. Try moving this up to where you say he shouts]
"Me?" he [s]replied[/s]asked [you should say "alex asked", since the last 'he' you mentioned was Ivan]. He started walking towards Ivan, this was his second mistake.
[s]But [/s]Ivan was quick and he lashed out to shove Alex against the wall, but his hand never made contact. Instead he doubled back in pain.[period] He looked one last time before he blacked out, for the boy, but all he saw was the end of a gun - and nothing.

The last sentence is a bit awkward. Maybe try 'He looked one last time for the boy before he black out, but all he saw was then end...'

^_^ Done!

This was pretty short, so I can't give you too much of a plot review, but what you have here is pretty good. You could benefit from a bit more description(maybe of what our assassin in thinking, maybe a recap on his plan? He's about to kill someone, isn't he checking out the scene to see if there are any hidden cops around??), but otherwise I think it's great. You have an interesting plot.

Good work.

^_^ Keek!

The ending's abrupt and effective.

This piece would really benefit from better spacing and a syntax/punctuation clean-up.

I agree with Sleeping Valour in that 'murder' seems like the wrong word here. 'Kill' would be more appropriate as it emphasises the cold premeditation of the act.

"Ivan made a bee-line for Alex" sounds rather artificial and stilted. Maybe: "Ivan (gathered pace as he) strode towards his target." Something like that.

Great start otherwise.

8.5/10

Well thanks for those, I'm going to make a rewrite. It was really a prolouge to a kind of murder mystery.

Hi Fang,
I liked this, it made me want to read more and find out what was going to happen (an effect of the nice cliffhanger ending!) My only concerns with it have already been named (I agree that the "bee-line" sentence doesn't quite work). I can't wait to read more!
~Keira