My husband is on call with Fauna Rescue because he has a Firearms Licence so he is often called to euthanase kangaroos that can't be treated. 
We received a call this morning from Diana Mc Gregor of Fauna Rescue about an injured kangaroo. This girl had a broken leg but was still mobile, she also had a Joey.
We had a hospital appointment in town in the morning.  So on our way to our appointment we went to find this poor girl. We spent some time looking but couldn't find her and as we were already very late we needed to go to my appointment and we were going to come back after and walk the scrub to see if we could find her. On the way to town I rang Dani and explained the situation and asked if there was any way they could also go look.  Dani had a vet appointment with one of their kangaroos that had hurt his back and wasn't getting better and unfortunately Dani didn't think they would be bringing him home.  So even though they had to make the heartbreaking decision about one of their kangaroos they still went out after they had been to the vet to look for the injured kangaroo.  Dani was going to ring me if they found her and keep an eye on her until we could get there.  We were an hour away from the location when I got a call from Dani saying they had sighted her, I told her we were on our way back and would be as quick as we could.  A short time later Dani rang back and told me that we didn't need to come after all. 

The following paragraph was a post Dani put on Facebook at the time explainibg how she rescued Conner.

After our appointment with the vet which concluded with our Charlie boy being euthanised due to severe renal failure, likely caused from myopathy, we headed out to the point where the injured female kangaroo had been seen.  After driving the area and being unable to find her I decided to walk the surrounding scrub.  I started from the furthest point that I thought she would be and did a grid/zigzag pattern through the scrub that met the road verge. About halfway down to the next corner, while looking for foot prints or drag marks I spotted a bright blue feather.  I followed the way it was pointing and came across an old kangaroo leg bone, pointing further away from the road and deeper into the scrub. I started walking in that direction and the female kangaroo must have heard me because she took off. I only caught a glimpse of her as she was over a crest but could tell she was injured. I called for my partner to bring the sedation and followed her. She became slightly entangled in a fence and I thought I would be able to catch her there but she got through and took off into a clear paddock.  As I jumped the fence I saw she had dropped her joey in the scuffle. Jarod picked him up while I followed her as she was travelling through the paddock very quickly. I called Rachael who was still about an hour away to come and shoot the injured female but as the kangaroo had already travelled about a km through the paddock and was nearing dense scrub which we would have lost her in, Jarod made to hard decision to euthanise her then and there.
It was horrible but she would have gotten away to die a slow horrible death. Her joey is a huge pinkie weighing in at 1500g and is very stressed and missing his mum still.

He has been named Conner and is being raised by Dani & Jarod, I swear sometimes the universe works in strange ways and even in times of heartbreak and horrible situations it gives you something you need to in order to mend your broken heart, and in this case it was Conner.
I had a case where I had one of my kangaroos (Brigalow) who was one of my favourites break his leg so badly that he had to be euthanised.  About two weeks after, a little male albino red came into care and even though Casper wasn't with us for very long as he ended up dying from health complications related to being an albino.  At the time Casper came in I believe he was one that the universe allowed me to care for me after losing my sweet boy Brigalow.
An injured kangaroo is often still very mobile and will fight till thier last breath for survival.  Native animals are designed to not show pain as one would expect because it makes them easy targets for predators.