Assuming that the perpetrator A is a robber with a knife and four people are slightly injured, then in the implementation of the act (objective act), it is a completed crime, which meets the objective elements of robbery and commits robbery.
Then, according to Article 17 of the Criminal Law, a person who has reached the age of 14 but under the age of 16 commits intentional homicide, intentional injury, serious injury or death, rape, robbery, drug trafficking, arson, explosion or poisoning, and shall bear criminal responsibility.
Therefore, although A is a person with limited capacity under 16 years old, he committed robbery in the above crimes, and there is no illegal obstacle (subjective element), which constitutes a crime.
Finally, according to the provisions of Article 72 of the Criminal Law, a criminal sentenced to criminal detention or fixed-term imprisonment of not more than three years may be suspended if he meets the following conditions, and a suspended sentence shall be announced for those under the age of 18, pregnant women and those who have reached the age of 75: (1) The circumstances of the crime are relatively minor; (2) showing repentance; (3) There is no danger of committing a crime again; (four) the announcement of probation has no significant adverse effects on the community where he lives.
However, the perpetrator is under the age of 18, has not caused "serious danger" (because the specific situation of the perpetrator is not provided, it is considered as "lighter"), and has not committed a crime again, showing repentance, and will be sentenced to probation and accepted community correction and other mechanisms.